Our review of elicitation and naturalistic studies of emotion response in schizophrenia reveals a number of important insights about emotional functioning among individuals with schizophrenia. By drawing upon the theories from affective science that point to the importance of distinguishing multiple components of emotion and the diverse methods for studying emotion, we can begin to pinpoint the nature of emotion response deficits in schizophrenia. Specifically, individuals with schizophrenia have a deficit in the expressive component but do not appear to be strongly deficient in the experiential and physiological components of emotion.
Across many different types of studies, individuals with schizophrenia do not exhibit many outwardly observable expressions in response to evocative stimuli or situations. Individuals with schizophrenia contract their facial musculature appropriately in response to positive and negative emotional stimuli, yet these contractions are not of sufficient magnitude to be observable to others. Diminished expressiveness is correlated with the symptom of flat affect and undoubtedly has important social consequences, though these have yet to be fully investigated. One interesting study that examined the social cost of inexpressiveness had individuals with and without schizophrenia discusses an emotionally evocative political topic.11
Consistent with other studies, individuals with schizophrenia were markedly less expressive during these interactions. However, their inexpressiveness evoked negative responses from their healthy interaction partners, but in terms of greater reports of sadness and fear and in terms of a “matching” of diminished expression by the healthy individuals over the course of the interaction. A significant proportion of the variance in healthy interaction partners’ facial expressions and reports of experienced emotion was accounted for by the lack of facial expressions among individuals with schizophrenia.
The findings on emotional experience in schizophrenia are more variable, but the majority of studies find that individuals with schizophrenia report comparable amounts of emotion compared with individuals without schizophrenia. At the outset, it is worth noting that the sample sizes were small in many of the studies reviewed, and thus, some studies may been underpowered to detect group differences in reported emotional experience. On the other hand, nearly all these studies demonstrated group differences in expressive behavior as well as differences in reported experience that varied by the valence of the presented stimuli. Thus, limited power cannot fully account for finding comparable reports of experience between individuals with and without schizophrenia.
A few studies (n = 4) find that individuals with schizophrenia report experiencing less pleasant emotion, rate positive stimuli as less pleasant (n = 6), or report less pleasant emotion in naturalistic settings (n = 3) compared with individuals without schizophrenia. At first glance, these findings appear to support the clinical conceptualization of anhedonia in schizophrenia. However, the bulk of studies (n = 26) find no differences in reports of pleasant emotion between individuals with and without schizophrenia. That most elicitation studies do not find evidence for a pleasure deficit in schizophrenia is consistent with other recent evidence that the nature of anhedonia in schizophrenia is not an “in-the-moment” or consummatory pleasure deficit but is instead an anticipatory pleasure deficit.45,85,99,134–136
A few elicitation and naturalistic studies have also found that individuals with schizophrenia experience more negative emotion relative to individuals without schizophrenia. This finding is consistent with studies assessing trait emotion experience in schizophrenia.27
(see also Horan et al29
). It may also be the case that the laboratory conditions in elicitation studies require more effort and concentration from individuals with schizophrenia, thus contributing to heightened reports of negative emotion and greater corrugator activity across differently valenced emotional stimuli.
Fewer studies have examined the physiological component of emotion among individuals with schizophrenia, and even fewer have assessed all 3 components of emotion response in the same sample. This remains a fruitful avenue for future research. Studies that have assessed emotion modulation of the startle response are consistent with studies that find few differences in emotional experience between individuals with and without schizophrenia. That is, individuals with schizophrenia are responding appropriately to the stimuli in these elicitation studies, both at the experiential and physiological levels.
As we have highlighted throughout the review, we know next to nothing about emotional responding among women with schizophrenia, and this remains an urgent need in the field. Based on the limited evidence available, it appears that women with schizophrenia may be more expressive than men with schizophrenia (though 2 studies suggest that women may be as equally inexpressive as men with schizophrenia) yet report comparable levels of emotion experience compared with men with schizophrenia and healthy individuals. Only one study has examined sex differences in physiology, and this study found no differences in emotion modulation of the startle among men and women with schizophrenia.91
This relative disregard for studying emotional responding among women with schizophrenia is all the more surprising given the accumulated evidence indicating that schizophrenia affects men and women differently. Compared with men, women have a later age of onset, a better course and medication response, better premorbid and social functioning, lower risk for obstetric complications, fewer structural brain abnormalities, and less language dysfunction.62,137–139
Some evidence suggests that women with schizophrenia may have more mood-related features, such as paranoia, dysphoria, or depression symptoms,140,141
whereas men with schizophrenia may have more negative symptoms, including flat affect,142
though other studies fail to find this pattern.143
Furthermore, there is consistent evidence from affective science that indicates healthy men and women differ in components of emotional responding, including expressive behavior,126,127
emotion modulation of the startle response,144,145
and neuroendocrine function.146
The relative dearth of knowledge about schizophrenia women's emotional responding despite the frequency with which women suffer from schizophrenia as well as the evidence highlighting important sex differences in emotion among healthy individuals point to the importance of this area of research.
Another area that has not been fully investigated is the extent to which different subgroups of individuals with schizophrenia may exhibit different emotion response deficits. As noted earlier, some studies suggest that individuals with the deficit syndrome experience less negative emotion than individuals with the nondeficit syndrome,22
though other studies do not find differences in reported emotional experience between individuals with and without the deficit syndrome.43
More broadly, however, the variability of findings on emotional experience in schizophrenia suggests that there well may be important differences among particular groups of schizophrenia individuals or in particular contexts that have yet to be fully investigated.
For the promise of affective science to be more fully realized in the realm of schizophrenia research, it will be important to address why individuals with schizophrenia exhibit a disconnect between the expression and experience of emotion. Research thus far has worked toward solving the puzzle of why individuals with schizophrenia are not very outwardly expressive. The expressive deficit does not appear to be a function of medication status, as individuals with schizophrenia who are not taking medication also exhibit diminished expressive behavior,45
nor does it appear to be redundant with a social skills deficit49
or a neuromotor deficit (eg, Putnam and Kring148
). That individuals with schizophrenia display subtle, microexpressions in response to emotional stimuli suggests the possibility that they have a different threshold for producing observable emotional displays and do so only when stimuli are of sufficient intensity.10
Indeed, individuals with schizophrenia are better able to pose facial expressions following the presentation of a pictured facial expression and to perceive emotion in faces when the facial stimuli depict intense expressions.148,149
Perhaps the greatest purchase toward answering the question of why individuals with schizophrenia exhibit a disconnect between emotion expression and experience may be obtained by integrating studies of emotion and cognition. For example, to understand the nature of an anticipatory pleasure deficit, studies must explicitly link the study of emotion and cognition. Indeed, recent evidence from cognitive neuroscience suggests that anticipating future events relies upon the same neural processes involved in episodic memory.150,151
In memory tasks, schizophrenia patients have difficulty in both recalling past episodes and in generating specific future events, particularly goal-directed events.134,152
Thus, understanding anticipatory pleasure deficits in schizophrenia will be bolstered by studying interrelated cognitive processes and the attendant brain areas that support such processes known to be deficient in schizophrenia, including cognitive control and episodic memory.
There are a number of important treatment implications that follow from the findings of this review. First, targeting specific components of emotion response will likely be an effective strategy, whether this is done pharmacologically or psychosocially. Second, adoption of the methods from affective science can be usefully incorporated into clinical trials to assess the effectiveness of various interventions in targeting emotion response difficulties.99,153
Third, different intervention approaches may be needed for men and women with schizophrenia,154
though the nature of sex differences in emotional responding remains to be borne out by additional research. Efforts are already underway to develop psychosocial treatments to address negative symptoms, such as flat affect and anhedonia,155
and the treatment of negative symptoms pharmacologically remains an unmet need and looming challenge in the field. 156–158
In summary, the proliferation of findings from affective science and neuroscience has greatly expanded our understanding of emotion response deficits in schizophrenia. Nevertheless, much work remains to be done. The adoption of clear and consistent terms, methods, and measures in both behavioral and brain imaging studies will quicken the pace of collective research on emotion in schizophrenia. Moreover, inclusion of women with schizophrenia in studies of emotion ought to be a top priority for the field, not an afterthought or mere concession to grant funding agencies. Continued efforts to translate methods and theories from affective science and cognitive neuroscience will undoubtedly help us better understand the descriptions, causes, and specific treatment targets for emotion response deficits in schizophrenia. It is our view that the goal of reducing the burden of schizophrenia is within reach, particularly with respect to ameliorating emotion response deficits.